Lineage from Eohippus to Pliohippus
History of the Horse



The history of the horse commenced in North America with horse-like mammals of many and various forms dating back as far as 55 million years.

These periods were divided into three periods—the Eocene, Miocene, and Pliocene or early, middle, and later.

These ancient horses all became extinct before the discovery of the country. Their abundant remains furnish the materials for marking out the genealogy of the horse.

They 1st roamed the North American plains all those years ago as Eohippus which was very small about the size of a fox and had four toes in front.


The Mesohippus lasted into the Miocene period and was the size of a sheep, and had three usable toes.

The Mesohippus, Miohippus Merychippus and Pliohippus were to follow with the Pliohippus looking similar to the small horses of Mongolia.

Studying fossils has shown that the oldest fossils of the horse on this continent all had many toes, and were small.

During their development they increased in size and reduced the number of toes, until modern Equus.

Their genealogy has been made through several successive stages, and the fossil prove its validity.

The figure shown below illustrates the successive changes of the fore-foot of these quadrupeds.

The lineage of the horse is derived from an original ancestor having five toes on each foot, but the parent of the race has not yet been discovered.

PSM V16 D273 Evolution of horse hoof.jpg
Ancient Horse’s toes


The splint-bone of the Miohippus is reduced to a short remant.

During the Pliocene, a 3 toed horse called the Protohippus, was the size of a donkey and large in number.  Still higher up, and a near ally of the modern horse was the Pliohippus made his appearance.

The series is completed in the subsequent appearance of a true Equus, as large as the existing horse.